Method of making hydroprocessing catalyst

ABSTRACT

A chelated hydroprocessing catalyst exhibiting low moisture is obtained by heating an impregnated, calcined carrier to a temperature higher than 200° C. and less than a temperature and for a period of time that would cause substantial decomposition of the chelating agent.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/086,535, filed on Aug. 21, 2009, which application is a nationalstage of PCT/US06/46947 filed Dec. 11, 2006, which application claimsthe benefit of Provisional Application No. 60/714,545, filed Dec. 14,2005, the disclosures of which are hereby incorporated herein byreference.

BACKGROUND

This patent relates to catalysts supported on a foraminous carrier andmethods for preparing such catalysts using stabilized aqueouscompositions. In particular, this patent relates to aqueous compositionscontaining catalytically-active metal components and substantially watersoluble acidic components and to the catalysts prepared using suchaqueous compositions for impregnating foraminous carriers. It isdesirable to convert heavy hydrocarbon feeds, including those having aboiling point below about 1200° F., into lighter, and more valuable,hydrocarbons. It is also desirable to treat hydrocarbon feedstocks,including petroleum residues, also known as resid feedstocks, in orderto carry out, for example, hydrodesulfurization (HDS),hydrodenitrogenation (HDN), carbon residue reduction (CRR),hydrodemetallation (HDM), including the removal of nickel compounds(HDNi) and vanadium compounds (HDV). The catalysts of the presentinvention are particularly useful and effective in thehydrodesulfurization, hydrodenitrogenation, hydrodemetallation, etc. ofpetroleum compositions, including high-boiling petroleum compositions.

Catalysts comprising at least one Group VIII metal component, at leastone Group VIB metal component and a phosphorus component, suchcomponents being carried on a foraminous carrier, are known in the art.

It is known that the metals of Group VIB of the periodic table, forexample, tungsten and molybdenum, and components comprising such metals,for example, compounds such as the oxides and sulfides, are active incatalyzing a wide variety of reactions including among others,hydrogenation, dehydrogenation, oxidation, desulfurization,denitrogenation, isomerization and cracking. However, catalytic metalsand components containing them are relatively costly and have arelatively small surface area per unit weight, so that they aretypically not used without resort to carrier materials. Consequently,these catalytically active metals or components are usually applied in adiluted form to the surface of a foraminous support material. Theforaminous support material is usually of a lower order of activity whencompared to the catalytically-active components, or such carriers mayeven be catalytically completely inactive.

Furthermore, it is known that certain metal-containing components ofGroup VIII of the periodic table of the elements, such as iron, cobalt,and nickel, when used in combination with the Group VIB metal-containingcomponents, result in enhanced catalytic activity. These Group VIIIcomponents are sometimes referred to as catalyst “promoters.” However,problems can result when these promoters are attempted to be impregnatedinto a carrier along with the catalytically active components of GroupVIB. Simple and direct impregnation techniques using a mixture of bothcomponents typically cannot be employed. For example, a combination ofcomponents based on cobalt or nickel salts with molybdenum or tungstencomponents typically results in unstable solutions, e.g., solutionssubject to the formation of precipitates. Impregnation of a carrierusing separate solutions comprising components of Group VIB and GroupVIII is not an acceptable alternative since that can result in costly,multi-step processes and ineffective or non-uniform metals distribution.

Rather costly and involved processes have been devised in order toobtain a uniform distribution throughout the available surface area ofthe foraminous catalyst carrier material when using componentscontaining both of the catalytically active metals of Group VIB andGroup VIII. It has been the objective of these methods to preparesolutions containing metals of both Group VIB and Group VIII that aresufficiently concentrated and of the requisite stability to allowsubsequent uniform impregnation and distribution of the metalsthroughout and upon the surface area of the carrier. These methodstypically include the use of high concentrations of phosphoric acid.Typically, the carrier is impregnated with a dilute solution comprisinga phosphorus component, although some applications do not use aphosphorus component, and components of metals of both Group VIB andGroup VIII, by applying the solution to a calcined foraminous carriermaterial, and then drying and calcining the composite to convert thecatalytically active material to other forms, particularly to the oxide.However, the use of phosphoric acid, particularly at high concentrationsthat are required to readily solubilize both of the metal containingcomponents and maintain them in a stable solution, can introduceperformance related problems during the use of such catalysts inhydroconversion processes.

Furthermore, there is increased interest in producing very low sulfurand nitrogen crude oil fractions and in producing and upgrading lowerquality hydrocarbon feeds, such as synthetic crudes and heavy petroleumcrude oil fractions. Unfortunately, high concentrations of nitrogen,sulfur, metals and/or high boiling components, for example, asphaltenesand resins, in such lower quality feeds render the same poorly suitedfor conversion to useful products in conventional petroleum refiningoperations. In view of such difficulties, lower quality hydrocarbonfeeds often are catalytically hydrotreated to obtain materials havinggreater utility in conventional downstream refining operations.Catalytic hydrotreating or hydroconversion involves contacting such afeed with hydrogen at elevated temperature and pressure in the presenceof suitable catalysts. As a result of such processing, sulfur andnitrogen in the feed are converted largely to hydrogen sulfide andammonia which are easily removed. Aromatics saturation and cracking oflarger molecules can also be used in order to convert high boiling feedcomponents to lower boiling components. Metals content of the feeddecreases as a result of deposition of metals on the hydrotreatingcatalyst.

As can be appreciated, satisfactory operation in processing feedscontaining high levels of impurities under severe process conditionsplaces increased demands on the catalyst to be employed as the same mustexhibit not only high activity in the presence of impurities and undersevere conditions, but also stability and high activity maintenanceduring the time that it is in use. Catalysts containing a Group VIBmetal component, such as a molybdenum and/or tungsten component,promoted by a nickel and/or cobalt component and supported on a porousrefractory inorganic oxide, are well known and widely used inconventional hydrotreating processes; however, the same often aresomewhat lacking in stability and activity maintenance under severeconditions.

It is known that preparation of hydrotreating catalysts containing GroupVIB and Group VIII metal components supported on a porous refractoryinorganic oxide can be improved through the use of phosphoric acidimpregnating solutions of precursors to the Group VIB and Group VIIImetal components or the use of phosphoric acid as an impregnation aidfor the metal precursors. Thus, Pessimisis, U.S. Pat. No. 3,232,887discloses stabilization of Group VIB and Group VIII metal-containingsolutions through the use of water-soluble acids. According to thepatentee, in column 3, lines 6-11, “in its broadest aspect the inventioncomprises the preparation of stabilized aqueous solutions which comprisean aqueous solvent having dissolved therein catalytically activecompounds containing at least one element from Group VIB of the periodictable and one element from Group VIII.” Inorganic oxyacids of phosphorusare included among the disclosed stabilizers, and the examples ofPessimisis illustrate preparation of various cobalt-molybdenum,nickel-molybdenum, and nickel-tungsten catalysts using phosphorus andother acids as stabilizers. Hydrodesulfurization results with certain ofthe cobalt-molybdenum catalysts are presented, and the patentee suggeststhat the use of the stabilized solutions may lead to improvedhydrodesulfurization activity in some instances.

Other patents relating to hydroconversion or hydrotreating processesdisclose various catalysts, their method of preparation as well as theiruse in such processes. For example, Simpson et al., U.S. Pat. No.4,500,424 and its divisional patent, U.S. Pat. No. 4,818,743 aredirected to hydrocarbon conversion catalysts containing at least oneGroup VIB metal component, at least one Group VIII metal component, anda phosphorus component on a porous refractory oxide having a defined andnarrow pore size distribution. The catalyst is said to be useful forpromoting various hydrocarbon conversion reactions, particularlyhydrodesulfurization. Similarly, Nelson et al., U.S. Pat. No. 5,545,602is directed to hydrotreatment of heavy hydrocarbons to increase contentof components boiling below 1000° F. by contact with Group VIIInon-noble metal oxide and Group VIB metal oxide on alumina havingspecific and defined surface area and pore size distribution. Thispatent also teaches, at column 9, lines 36-37, to avoid addingphosphorus-containing components during catalyst preparation because“Presence of phosphorus undesirably contributes to sediment formation.”In furtherance of this teaching it is suggested, at lines 54-57, thatimpregnating solutions may be stabilized with H₂O₂ so that solutionsstabilized with H₃PO₄ not be used. See also Dai et al., U.S. Pat. Nos.5,397,956 and 5,498,586 similarly directed to defined carrier propertiesfor improved hydroconversion catalysts.

In the catalysts of the present invention, the metals are typicallyactivated by converting them into the corresponding metal sulfides. Thiscan be accomplished by introducing the catalyst comprising theimpregnated metals in a device or reactor and conducting a suitablepre-sulfurization treatment, wherein the catalyst layer is sulfurized byintroducing a hydrocarbon oil containing an appropriate sulfurizingagent at elevated temperature. The active site of the thus-pretreatedcatalyst is formed on the surfaces of the resulting active metalsulfides so that the total number of active sites increases with anincrease in the exposed surface area of the active metal sulfides,yielding a high catalyst activity. An increase in exposed surface areaof the active metal sulfides may be attained by enhancing dispersion ofthe active metal sulfides as carried on the catalyst carrier or byminimizing the crystal size of the respective active metal sulfides.Methods for preparing such a catalyst include dipping a catalyst carrierin an aqueous solution of active metals containing a carboxylic acid,such as citric acid or malic acid, as a complexing or chelating agentfor active metals and thereafter firing the impregnated carrier. Forexample, EP 0181035(A2) discloses a method of preparing a catalyst inwhich an organic compound having a nitrogen-containing ligand (e.g.,amino group, cyano group) such as nitriloacetic acid,ethylenediaminetetraacetic acid or diethylenetriamine is used as acomplexing agent and is added to an aqueous solution of active metals, acatalyst carrier such as an alumina or silica is dipped in the resultingaqueous solution of active metals, and the catalyst composed of activemetals carried on the catalyst carrier is then dried at a temperature ofnot higher than 200° C. without firing. Similar methods are disclosed inU.S. Pat. No. 5,200,381 wherein the complexing agent is ahydroxycarboxylic acid, for example citric acid, and the agent is usedin solution with the active metals and the resulting impregnated carrieris kneaded and shaped; or in U.S. Pat. No. 5,232,888 the agent is addedto a catalyst already containing the active metals deposited on acarrier. In both of these patents the resulting composition is heatedand dried at a temperature not higher than 200° C., and in the absenceof calcination, in order to avoid decomposition of the complexing agent.

In accordance with the method of adding a hydroxycarboxylic acid as acomplexing agent followed by firing, the acid can be effective forincreasing the stability of the active metal-dipping solution as it actsas a complexing agent for active metals and additionally the acid isalso effective for inhibiting coagulation of active metals. However, theactive metals are subject to coagulation because of the final firingstep thereby tending to decrease catalyst activity. On the other hand,in accordance with the method disclosed in EP 0181035(A2), since theactive metal ions such as Mo or Ni ions are firmly coordinated with thenitrogen-containing compound, such ions are carried on the carrier in ahighly dispersed condition. In addition, since the catalyst containingthe active metals is not calcined but is merely dried at a lowtemperature, not higher than 200° C., and since sulfurization isconducted with unoxidized metals, the active metals can be maintained ina dispersed state. While such catalysts exhibit desirably high activity,they are deficient in that the low temperature heating and drying stepdoes not remove sufficient water, thereby requiring that such water beremoved during the initial stages of hydroprocessing, an undesirable andburdensome characteristic. In particular, the water driven off at thisearly stage in the use of the catalyst can place an undue burden onplant equipment that separates water from the processed petroleumfractions.

Notwithstanding the diverse teachings of patents and publications inrespect of the preparation of hydroprocessing or hydrotreatingcatalysts, there is a continuing need for development of improvedcatalysts, particularly catalysts that are effective but contain lowerlevels of moisture as delivered to the petroleum processor.

SUMMARY OF THE INVENTION

Embodiments of the invention comprise a hydroprocessing catalyst andmethod for preparing such catalyst comprising: (I) providing at leastthe following components: (A) at least one calcined foraminous carrierhaving a water pore volume; (B)catalytically active metals useful inhydroprocessing hydrocarbons, said metals in the form of at least onecomponent providing at least one metal from Group VIB of the periodictable and at least one component providing at least one metal from GroupVIII of the periodic table; (C) at least one chelate; (D) water in aquantity sufficient to form a solution or dispersion comprising saidcatalytically active metals and said at least one chelate; and (E)optionally, at least one phosphorus-containing acidic component; (II)contacting said components (I)(A) with said solution or dispersioncomprising (I)(B), (I)(C) and optionally (I)(E) for a time and at atemperature sufficient to form a mixture and to impregnate said carrierwith a suitable amount of said components (I)(B) and (I)(C); (III) tothe extent that the volume of said solution or dispersion equals orexceeds the water pore volume of said carrier separating saidimpregnated carrier; and (IV) heating said impregnated carrier to atemperature higher than 200° C. and less than a temperature and for aperiod of time that would cause substantial decomposition of said atleast one chelate. An exceptionally dry catalyst having desirableactivity is obtained even in the absence of calcining followingimpregnation.

DETAILED DESCRIPTION OF THE INVENTION

In the specification and in the claims, the singular forms “a”, “an” and“the” include the plural unless the context clearly dictates otherwise.For purposes of the present invention, unless otherwise defined withrespect to a specific property, characteristic or variable, the term“substantially” as applied to any criteria, such as a property,characteristic or variable, means to meet the stated criteria in suchmeasure such that one skilled in the art would understand that thebenefit to be achieved, or the condition or property value desired ismet. The term “about” when used as a modifier for, or in conjunctionwith, a variable, is intended to convey that the numbers and rangesdisclosed herein are flexible and that practice of the present inventionby those skilled in the art using, e.g., temperatures, concentrations,amounts, contents, carbon numbers, properties such as particle size,surface area, pore diameter, pore volume, bulk density, etc., that areoutside of the range or different from a single value, will achieve thedesired result, namely, an effective hydroprocessing catalyst exhibitinglower levels of moisture as made compared to catalysts of the prior artcomprising similar active metals and other components and heated withoutcalcining.

Throughout the entire specification, including the claims, the word“comprise” and variations of the word, such as “comprising” and“comprises,” as well as “have,” “having,” “includes,” “include” and“including,” and variations thereof, means that the named steps,elements or materials to which it refers are essential, but other steps,elements or materials may be added and still form a construct within thescope of the claim or disclosure. When recited in describing theinvention and in a claim, it means that the invention and what isclaimed is considered to be what follows and potentially more. Theseterms, particularly when applied to claims, are inclusive or open-endedand do not exclude additional, unrecited elements or methods steps.

All references herein to elements or metals belonging to a certain Grouprefer to the Periodic Table of the Elements and Hawley's CondensedChemical Dictionary, 13^(th) Edition. Also, any references to the Groupor Groups shall be to the Group or Groups as reflected in this PeriodicTable of Elements using the CAS system for numbering groups.

The general procedures for preparing impregnating solutions ofcatalytically active metals are described in detail by D. Klein inpatent application US 2005/0109674, published May 26, 2005, which is acontinuation in part of application Ser. No. 10/719,551, filed Nov. 20,2003. The content of each of these published and filed applications isincorporated herein.

“Post-impregnated” catalyst refers to a catalyst in which themetals-containing solution or solutions are added after the foraminouscatalyst carrier is calcined. The foraminous catalyst carrier can becalcined before or after shaping of the catalyst particle, but theimportant aspect is that the metals-containing solution or solutions beadded after the carrier material is calcined. Thus, a “post-impregnated”catalyst can be made as follows:

Uncalcined pseudoboehmite alumina powder is thoroughly mixed with water,or optionally with a dilute aqueous solution of nitric acid or anorganic acid such as acetic or formic acid, and the alumina mixture,containing about 50 to 65 weight percent moisture, is then formed intocatalyst particles having a desired size and shape, preferably byextrusion. The formed particles are dried at a temperature of about 110to about 150° C., and then calcined at a temperature of about 400 toabout 750° C. for about one to two hours. The dried and calcinedparticles are contacted with a suitable quantity of a stable metalssolution including a chelating agent as described in detail hereinbelow.For example, such solution typically contains molybdenum, nickel andphosphorus, or molybdenum, cobalt and phosphorus, plus an optionaladditional quantity of Group VIII metals solution, if required, in orderto provide the desired amount of metals on the finished catalyst, whilesubstantially and uniformly filling the pores. After a suitable contacttime, the formed catalyst particles are heated at an elevatedtemperature as described in detail hereinbelow to effectively removesubstantially all of the residual moisture without the need forcalcining, thus preserving the chelating agent, typically present as anorganic compound.

Suitable catalytically active elements or metals from Group VIII of theperiodic table present in components of the invention may include Fe,Co, Ni, Pd, Pt and the like and mixtures thereof. Of these, the mostpreferable are Co and Ni. Suitable Group VIB elements or metals includeCr, Mo, W, and mixtures thereof; most preferred are Mo and W. Preferredcombinations of metal components comprise, e.g., nickel and molybdenum,cobalt and molybdenum, tungsten and nickel or cobalt, molybdenum and acombination of cobalt and nickel, tungsten and a combination of nickeland cobalt, a combination of molybdenum and chromium and nickel, etc;the combination of molybdenum and nickel is particularly preferred.

The overall process for preparing a stable impregnating solution can bedescribed as follows:

An amount of a substantially water-insoluble Group VIII metal componentis added to water to form a slurry. The amount of the Group VIII metalcomponent is low relative to the amount of the Group VIB metal componentthat will be added in a subsequent step. The specific amount of thesubstantially water-insoluble Group VIII metal component can becharacterized by the molar ratio of the Group VIII metal to the GroupVIB metal in the final impregnating solution; typically, the molar ratiois from about 0.05 to about 0.75; other suitable ranges of this variableand others are described below.

To the aqueous slurry of the substantially water-insoluble Group VIIImetal component just described, is added an aqueous solution of awater-soluble, phosphorus-containing acidic component. The amount ofthis acidic phosphorus component is low relative to the amount of theGroup VIB metal component that will be added in a subsequent step, andis at a level that may be insufficient to cause the Group VIII metalcomponent to become substantially soluble at this stage of the process,although it is believed that the components added in these steps 1 and 2undergo reaction. In any event, a slurry of the components is maintainedat this stage. The specific amount of the water-soluble,phosphorus-containing acidic component can be characterized by the molarratio of elemental phosphorus to the Group VIB metal in the finalimpregnating solution; typically this molar ratio is from about 0.01 toabout 0.80.

To the aqueous slurry present at the end of step 2, is added the GroupVIB metal component. In step 3 the resulting slurry mixture is heatedfor a time and to a temperature sufficient for the Group VIB metalcomponent to react with the aqueous slurry produced by the substantiallywater-insoluble Group VIII metal component and the water-soluble,phosphorus-containing acidic component, and to form a solution.Generally, mixing and heating may be carried out over a period of about1 to about 8 hours and at a temperature of about 160 to about 200° F.

The concentration of the Group VIB metal component in the impregnatingsolution composition can be quite high, up to about 50 weight percent,expressed as the oxide, and based on the total weight of theimpregnating solution composition. It should be obvious to those skilledin the art that more dilute solutions, useful for particularapplications, can be obtained by diluting the concentrated compositionwith a suitable amount of water.

Additional Group VIII metal, in the form of a substantiallywater-soluble Group VIII metal component, can be added to thecompositions in step 4 as required to give the desired level of GroupVIII metal component and the desired ratio of Group VIII metal componentto Group VIB metal component in the finished catalyst. The molar ratioof Group VIII metal component to Group VIB metal component can thus bevaried from about 0.05 to about 1.0.

Furthermore, a chelating agent, preferably citric acid, is added to thecomposition as well. Preferably the citric acid is added in twoportions, one to the water prior to addition of the metals and a second,larger portion after addition of the metal compounds. Typically, theratio of citric acid added at the beginning to that added at the end isabout 1:99 to about 35:65; preferably about 20:80 to about 30:70. Wherea split addition of the chelating agent is used, the second portion isadded to the solution that is at a temperature typically of from aboutambient to less than about 150° F.; preferably less than about 140° F.;more preferably less than about 130° F.

The catalyst impregnating compositions produced by the method described,allow for high concentrations of the Group VIB metal component at lowrelative concentrations of both the phosphorus and Group VIII metalcomponents. The low relative concentration of the phosphorus componentcan be advantageous for the preparation of catalysts that can benefitfrom or tolerate a low level of phosphorus. Additionally, this catalystimpregnating solution is surprisingly stable, i.e., it can be stored forextended periods as a solution without the formation of precipitates.

The low relative concentration of the Group VIII metal component isadvantageous for several reasons. First, the compositions allow for thepreparation of catalysts with a wide range of ratios of Group VIII metalcomponent to Group VIB metal component. Second, a substantial amount ofthe Group VIII metal component required for the finished catalyst can beadded in the form of a substantially water-soluble Group VIII metalcomponent that might otherwise be difficult to solubilize in thepresence of a large amount of Group VIB metal component unless asignificantly larger amount of the acidic phosphorus component was used.These substantially water-soluble Group VIII metal components,especially the salts of mineral acids (e.g., nitrates), can be morecost-effective than the substantially water-insoluble Group VIII metalcomponent salts (e.g., carbonates). Third, controlled heating of theimpregnated catalyst at elevated temperature facilitates removal ofmoisture from the catalyst without calcining, thus preserving thechelating agent and reducing the adverse impact of excessive moistureduring start-up when the catalyst is used in hydroprocessing orhydroconversion operations. Fourth, as will be described andexemplified, the impregnating solution of the present invention can beused to produce a hydroconversion catalyst having excellent performancecharacteristics.

Suitable Group VIII metal components for use in the invention which arecharacterized herein as substantially insoluble in water include thecitrates, oxalates, carbonates, hydroxy-carbonates, hydroxides,phosphates, phosphides, sulfides, aluminates, molybdates, tungstates,oxides, or mixtures thereof. Oxalates, citrates, carbonates,hydroxy-carbonates, hydroxides, phosphates, molybdates, tungstates,oxides, or mixtures thereof are preferred; most preferred arehydroxy-carbonates and carbonates. Generally, the molar ratio betweenthe hydroxy groups and the carbonate groups in the hydroxy-carbonate isin the range of about 0-4; preferably about 0-2; more preferably about0-1; and most preferably about 0.1-0.8. In particular, suitablesubstantially water insoluble components providing a Group VIII metalare the oxide, carbonates and hydroxides of nickel and cobalt.

Suitable substantially water-soluble components providing a Group VIIImetal for use in the invention include salts, such as nitrates, hydratednitrates, chlorides, hydrated chlorides, sulfates, hydrated sulfates,formates, acetates, or hypophosphite. Suitable substantiallywater-soluble nickel and cobalt components include nitrates, sulfates,acetates, chlorides, formates or mixtures thereof, as well as nickelhypophosphite. Suitable water-soluble iron components include ironacetate, chloride, formate, nitrate, sulfate or mixtures thereof. Inparticular, substantially water-soluble components are salts such asnickel and cobalt nitrates, sulfates, and acetates.

An indicator of the relative solubility of the substantially insolubleand soluble components can be found by comparing nickel carbonate tonickel nitrate or nickel sulfate. As reported in the CRC Handbook ofChemistry and Physics, 69^(th) Ed., 1988-9 (R.C. Weast, Ed., CRC Press),nickel carbonate has a solubility of about 0.009 g/100 mL of waterwhereas nickel nitrate has a solubility of about 239 g/100 mL and nickelsulfate a solubility of about 29-76 g/100 mL, depending on the water ofhydration of the particular salt. Furthermore, the solubility of thesulfate salts increases to about 87-476 g/100 mL in hot water.Consequently, one skilled in the art will understand the reference to“substantial” with regard to water solubility of these components.Alternatively, for purposes of the present invention, the aqueoussolubility of a substantially water insoluble Group VIII metal componentis generally less than 0.05 moles/100 mL (at 18° C.); conversely, thesolubility of a substantially water-soluble component is greater than0.05 moles/100 mL, e.g., greater than about 0.10 moles/100 mL (at 18°C.).

Suitable components providing a Group VIB metal include bothsubstantially water-soluble and substantially water insolublecomponents. Suitable substantially water-soluble Group VIB metalcomponents include Group VIB metal salts such as ammonium or alkalimetal monomolybdates and tungstates as well as water-solubleisopoly-compounds of molybdenum and tungsten, such as metatungstic acid,and metatungstate salts, or water-soluble heteropoly compounds ofmolybdenum or tungsten comprising further, e.g., P, Si, Ni, or Co orcombinations thereof. Suitable substantially water-soluble isopoly- andheteropoly compounds are given in Molybdenum Chemicals, Chemical dataseries, Bulletin Cdb-14, February 1969 and in Molybdenum Chemicals,Chemical data series, Bulletin Cdb-12a-revised, November 1969. Suitablesubstantially water-soluble chromium compounds include chromates,isopolychromates and ammonium chromium sulfate. Suitable Group VIB metalcomponents that are substantially water insoluble, e.g., having a lowsolubility in water, include di- and trioxides, carbides, nitrides,aluminium salts, acids, sulfides, or mixtures thereof. Preferredsubstantially insoluble Group VIB metal components are di- andtrioxides, acids, and mixtures thereof. Suitable molybdenum componentsinclude molybdenum di- and trioxide, molybdenum sulfide, molybdenumcarbide, molybdenum nitride, aluminium molybdate, molybdic acids (e.g.H₂MoO₄), ammonium phosphomolybdate, ammonium di- and hepta-molybdate, ormixtures thereof; molybdic acid and molybdenum di- and trioxide arepreferred. Suitable substantially insoluble tungsten components includetungsten di- and trioxide, tungsten sulfide (WS₂ and WS₃), tungstencarbide, orthotungstic acid (H₂WO₄.H₂O), tungsten nitride, aluminiumtungstate (also meta- or polytungstate), ammonium phosphotungstate, ormixtures thereof; ammonium metatungstate, orthotungstic acid andtungsten di- and trioxide are preferred. Most preferred is molybdenumtrioxide, MoO₃. For purposes of the present invention, the aqueoussolubility of a substantially water insoluble Group VIB metal componentis generally less than 0.05 moles/100 mL (at 18° C.); conversely, thesolubility of a substantially water-soluble component is greater than0.05 moles/100 mL, e.g., greater than about 0.10 moles/100 mL., theoxides such as molybdenum trioxide, molybdenum blue, also identified asmolybdenum pentoxide, tungstic oxide, etc.; the acids, e.g., molybdic,tungstic and chromic acids; metal salts such as the ammonium, alkali andalkaline earth metals, e.g., ammonium heptamolybdate, ammoniumphosphomolybdate, ammonium paratungstate; and the complex salts of GroupVIB and Group VIII metals such as complex cobalt and nickelphosphomolybdates.

The phosphorus-containing acidic component is substantially watersoluble, preferably a water soluble, acidic component that may be anoxygenated inorganic phosphorus-containing acid such as phosphoric acidalthough any one or more of the phosphoric acids may be used, includingorthophosphoric acid, metaphosphoric acid, pyrophosphoric acid,triphosphoric acid and tetraphosphoric acid and mixtures thereof. Forthe purposes of the invention, substantial phosphorus water solubilitymeans sufficient solubility to react with the substantiallywater-insoluble Group VIII metal component. Additionally, a soluble saltof phosphoric acid, such as the ammonium phosphates may also be used.Phosphoric acid may be added to the solution in liquid or solid form. Apreferred compound is orthophosphoric acid (H₃PO₄) in a highlyconcentrated aqueous solution, although any suitable form of phosphoricacid or precursor thereof, e.g., phosphorus pentoxide (P₂O₅) may beutilized. Naturally, concentrated acid may be appropriately diluted foruse or an appropriate form of dilute acid may be used directly.

Should it be desired to supplement the composition with an acid, e.g.,in order to adjust the pH, other suitable, water-soluble acids can beused, such as a hydroxy monocarboxylic acid, a polyhydroxymonocarboxylic acid, a hydroxy polycarboxylic acid, a polyhydroxypolycarboxylic acid, a monocarboxylic acid, etc.

The catalyst composition typically comprises (on a dry weight basis)about 5 to about 50 wt % of the total of Group VIB and Group VIII metalcomponents, calculated as oxides based on the total weight of thecatalyst composition; preferably, about 8 to about 45 wt %, morepreferably about 10 to about 40 wt %. The amount of Group VIB metals andGroup VIII metals can be determined using atomic absorption spectrometry(AAS), inductively-coupled plasmaspectrometer (ICP) analysis and/orx-ray fluorescence (XRF).

Examples of suitable foraminous carrier materials include silica, silicagel, silica-alumina, alumina, titania, titania-alumina,zirconia-alumina, zirconia, boria, terrana, kaolin, magnesium silicate,magnesium carbonate, magnesium oxide, aluminum oxide, precipitatedaluminum oxide, activated alumina, bauxite, kieselguhr, pumice, naturalclays, synthetic clays, cationic clays or anionic clays such assaponite, bentonite, kaolin, sepiolite or hydrotalcite, and mixturesthereof. Preferred foraminous carrier components are silica,silica-alumina, alumina, titania, titania-alumina, zirconia, bentonite,boria, and mixtures thereof; silica, silica-alumina, and alumina areespecially preferred. Alumina can be prepared, e.g., by converting analumina precursor such as boehmite, into a preferred carrier materialgamma-alumina.

As described above, in the catalyst compositions according to theinvention, the metal components are converted partly or wholly intotheir sulfides. This can be accomplished by introducing the catalystcomprising the impregnated metals in a device or reactor and conductinga suitable pre-sulfurization treatment, wherein the catalyst issulfurized by introducing a petroleum or hydrocarbon oil containing anappropriate sulfurizing agent at elevated temperature. In that case, itis preferred for the catalyst to be essentially free from Group VIIImetal disulfides. This step is typically carried out at the time thatthe catalyst is put into use for conducting hydroprocessing operations.However, catalysts of the prior art containing a chelating agent whereinthe catalyst had not been calcined after impregnation typicallycontained high residual moisture. Such moisture presented an undueburden on the process. That limitation is substantially overcome by thecatalysts prepared according to the methods of the present invention.

Embodiments of the present invention include:

(I) A stabilized composition adapted for use in impregnating catalystcarriers comprising: (A) water; (B) catalytically active metals being inthe form of and comprising: (1) at least one component providing atleast one metal from Group VIB of the periodic table; and (2) at leastone component providing at least one metal from Group VIII of theperiodic table; wherein (i) the Group VIII metal is provided by asubstantially water insoluble component; (ii) the molar ratio of theGroup VIII metal to Group VIB metal is about 0.05 to about 0.75,provided that the amount of the Group VIII metal is sufficient topromote the catalytic effect of the Group VIB metal; and (iii) theconcentration of the Group VIB metal, expressed as the oxide, is atleast about to about 50 weight percent based on the weight of thecomposition; and (C) at least one water soluble, phosphorus-containingacidic component in an amount sufficient to provide an elementalphosphorus to Group VIB metal molar ratio of about 0.01 to less thanabout 0.80. If it is desired to prepare a low metal concentrationcatalyst, the stabilized aqueous impregnating composition can have arelatively dilute concentration of the Group VIB metal expressed as theoxide, for example, from about 3 to about 6 weight percent; for example,about 3.5 to about 5.5 weight percent. In contrast, where a higher metalcontent catalyst is desired, the impregnating composition, expressed asthe oxide, can contain about 15 to about 50 weight percent of the GroupVIB metal; for example, about 18 to about 46 weight percent; or about 21to about 42 weight percent. Other useful compositions are found withinthe range of about 3 to about 50 weight percent of the Group VIB metalincluding, for example, 7-27, 8-30, 10-24 as well as concentrations inthe range of about 12 to about 48 weight percent; for example about 13to about 40 weight percent. Useful molar ratios of the Group VIII metalto Group VIB metal are about 0.05 to about 0.75; or about 0.15 to about0.65; for example, about 0.20 to about 0.60. Furthermore, the molarratio of elemental phosphorus to Group VIB metal can be about 0.01 toabout 0.80; or about 0.05 to about 0.76; for example, about 0.09 toabout 0.72.

The impregnating solution prepared in the sequence described in detailbelow is surprisingly stable and can be stored for an extended period oftime until needed to prepare the catalyst. The composition can be stablefor periods in excess of hours, days and weeks, even periods in excessof a month or more.

Where a catalyst is desired having a higher concentration of Group VIIImetal, e.g., nickel, the aqueous impregnating solution can besupplemented with a nickel component in soluble form. In that case, thetotal amount of Group VIII metal is increased and the molar ratio ofGroup VIII metal to Group VIB metal can typically range from about 0.05to about 1.0; preferably about 0.15 to about 0.9; more preferably about0.15 to about 0.8. As will be later described, the additional, solubleGroup VIII metal component can be included in the aqueous impregnatingsolution or, preferably, added as an aqueous solution to the combinationof foraminous carrier and impregnating composition described above.

The stable aqueous impregnating solution described in (I) above can beemployed in a process for preparing the catalyst of the presentinvention as follows: A mixture is prepared using the impregnatingsolution of (I), optionally a quantity of additional Group VIII metalcomponent in soluble form where the catalyst is to contain a higherlevel of the Group VIII metal than is available in (I) and a calcinedforaminous powder. It should be appreciated that alternative variationsare also feasible. For example, the soluble Group VIII metal componentcould be combined with (I) to provide the total amount of such metalrequired and that mixture could constitute one feed component.Alternatively, the calcined foraminous carrier could be combined withthe soluble Group VIII metal component and that mixture could becombined with (I) in the desired quantity. Alternative convenientarrangements will be apparent to a person skilled in the art. Thejust-described components are fed to a mixer, for example, a shortresidence time, low energy mixer or a higher energy mixing device inorder to combine these components. The carrier can be impregnated byvarious methods well known to those skilled in the art. For example, the“incipient wetness” or “dip-soak” techniques can be employed; thedip-soak method is preferred. In the incipient wetness method, thevolume of the metals-containing solution is adjusted, usually by addingadditional water, such that the volume is substantially the same as thepore volume of the carrier. In the dip-soak method the carrier is dippedat least once into a concentrated metals-containing solution (alsocontaining the chelating agent). The concentrations and relative ratiosof the metals and chelating agent in the first and subsequent dips canbe adjusted in order to achieve the concentration of each of the metalsand chelating agent that is desired in the final catalyst. In thedip-soak method the impregnated carrier is separated from the finalsolution, for example by draining, and in both techniques theimpregnated carrier is then heat treated at elevated temperature but inthe absence of calcination.

The method used to prepare the aqueous composition of (I) above isunique in that it results in a stable composition, as described, eventhough the amount of phosphorus-containing acidic component, e.g.,phosphoric acid, is insufficient to effect dissolution of thesubstantially water insoluble Group VIII metal component when the twoare combined. Another embodiment of the method can be generallydescribed as follows:

A method of preparing stabilized aqueous compositions for use inimpregnating catalyst carriers to produce catalysts useful in chemicallyrefining hydrocarbons, comprising adding to a suitable quantity ofwater: (A) a suitable amount of at least one chelating agent; (B) atleast one substantially water insoluble Group VIII metal component toproduce a slurry; (C) at least one substantially water soluble,phosphorus-containing acidic component in an amount insufficient tocause dissolution of the Group VIII metal component so as to produce aslurry and combining the slurry with; (D) at least one Group VIB metalcomponent; (E) mixing the combination of (A), (B), (C) and (D) and,heating the mixture, for a time and to a temperature sufficient for (A),(B), (C) and (D) to form a solution; and (F) adding an additional amountof water, if required, to obtain solution concentrations of the at leastone Group VIII metal, the at least one Group VIB metal and phosphorususeful for impregnating the carrier; wherein Group VIB and Group VIIIrefer to Groups of the periodic table of the elements. Useful amounts,concentrations and ratios of the components are as further described in(I) above. Typically, mixing and heating is carried out over a period ofabout 0.5 to about 16 hours; preferably about 1 to about 8 hours; morepreferably about 1 to about 4 hours; at a temperature typically about150 to about 220° F.; preferably about 160 to about 200° F.; morepreferably about 180 to about 190° F.

Complexing or chelating agents suitable for use in the present inventionare typically organic compounds and preferably include hydroxycarboxylicacids, especially those that contain one or more carboxyl groups and oneor more hydroxyl groups, for example, glycolic acid, hydroxypropionicacid, hydroxybutyric acid, hydroxyhexanoic acid, tartaric acid, malicacid, glyceric acid, citric acid, gluconic acid, saccharic acid,mandelic acid and the like. Other useful chelating agents include thosehaving chemical functional groups such as alcohol, including ethyleneglycol, glycerol, ethanol amine, poly ethylene glycol, hydroquinone;amine, including ethylenediamine, ethylenediamine-tetraacetic acid;sulfhydryl group, as found in the amino acid cysteine; carboxyl groupsin a variety of chemical substances: gluconic acid,pyridine-2,3-dicarboxylic acid, thiophene-2-carboxylic acid,mercaptosuccinic acid, nicotinic acid; amino acid, including alanine,methionine; sugar, including lactose; and ketone, includingacetone-1,3-dicarboxylic acid.

The amount of the chelating agent, preferably at least onehydroxycarboxylic acid, to be added to the catalyst is typically about0.05 to about 5 molar times of the total number of moles of the metalsof Group VIB and Group VIII; preferably about 0.15 to about 4; morepreferably about 0.2 to about 3. At concentrations significantly lessthan about 0.05 molar times, it is insufficient for forming a suitablecomplex of the active metals. However, at concentrations significantlygreater than 5 molar times, further improvement in activity is notlikely but there is a risk that the chelating agent can precipitatethereby clogging the pores of the carrier. While it is desired to avoidsubstantial degradation or decomposition of the chelating agent duringhigh temperature heating, it may be desirable to use an excess of thechelating agent, for example, citric acid, over and above the leveldesired in the final catalyst in order to compensate for the loss ofchelating agent that may occur during elevated temperature heating, suchas by decomposition. For purposes of the present invention avoidingsubstantial decomposition means retaining, after heating, about 85% ofthe chelate, for example citric acid, incorporated on or in the carrieror in combination with the metals; preferably retaining about 90%; morepreferably retaining about 95% of the citric acid. Such excess can beabout 1 wt % to about 10 wt %; preferably about 2 wt % to about 8 wt %;more preferably about 3 wt % to about 6 wt %; alternatively about 3 wt %to about 5 wt %.

The catalysts of the present invention are prepared by methodspreviously believed by those skilled in the art not to be available. Inparticular, a carrier, specifically a calcined foraminous carrier, isimpregnated with an aqueous composition comprising a mixture of activemetals and chelating agent, preferably at least one hydroxycarboxylicacid, and optionally a phosphorus-containing acidic component. If theimpregnation method results in an excess volume of solution compared tothe pore volume of the carrier (such as where the “dip-soak” method isused), the impregnated carrier is separated from the liquid, forexample, by draining. If impregnation is carried out using the“incipient wetness” method where little or no excess solution ispresent, it is not necessary to drain the impregnated carrier. In thenext step the impregnated carrier is placed in a heated environment, forexample on a moving bed that passes through an oven, a rotary calcineror any other convenient environment or vessel well-known to thoseskilled in the art. The wet, impregnated catalyst is then heated to atemperature higher than 200° C. (392° F.), but less than a temperaturethat would result in significant or substantial degradation of theorganic chelating agent. In other words, the functional integrity of thechelating agent is substantially maintained. A minor level ofdegradation of the chelating agent can be tolerated.

Various criteria can be used to ascertain a suitable heating time forthe impregnated carrier in order to achieve the benefits of the presentinvention. While it can be desirable to do so, it is not necessary todry the catalyst to the extent that all moisture is removed since doingso may require excessively long drying time at low temperature orexcessive degradation of the chelating agent at elevated temperatures.Furthermore, the temperature of the heating medium, typically airalthough other gasses, for example inert gasses such as nitrogen orcarbon dioxide, can be used as a measure of the temperature to which theimpregnated catalyst is heated. In some instances, such as when thecatalyst is heated for a short time and/or the layer of catalyst isrelatively thick, the temperature of the catalyst may not be the same asthat of the heating medium. In such circumstances the temperature of theheating medium can be used as a proxy for the temperature of thecatalyst and alternative criteria, such as discussed below can be usedto ascertain when a suitable catalyst is obtained. In one embodiment thecatalyst is typically heated to a temperature higher than 200° C. or392° F.; preferably equal to or greater than about 395° F.; morepreferably equal to or greater than about 398° F.; still more preferablyequal to or greater than about 400° F.; most preferably about 400° F. toabout 420° F.; alternatively about 400° F. to about 415° F.; or about400° F. to about 410° F.; and in each instance under conditions of timeand temperature such that substantial decomposition of the chelatingagent, for example citric acid, is avoided. Naturally, longer heatingtimes are feasible at the lower temperatures of those recited, buttypically heating is carried out for a period of time less than about 1hour; preferably less than about 30 minutes; more preferably less thanabout 10 minutes, and in each instance greater than about 1, 2, 3, 4 or5 minutes and for a total time at the selected temperature asappropriate to accomplish the benefits as further described below.

One criterion for establishing that a suitable catalyst has beenobtained is to measure the weight percent loss on ignition (LOI) of thecatalyst following preparation. LOI is a measure of the total volatilespresent in the sample, essentially water and the organic chelatingagent. The LOI test is conducted by subjecting a sample to anoxygen-containing atmosphere for 1 hour at 1020° F. (548.9° C.), therebyoxidizing or igniting the organic matter and driving off all residualmoisture in the catalyst. However, the temperature of the test isbelieved not to be sufficiently high to affect the inorganic components.Catalysts prepared according to the present invention have been observedto have LOI values typically less than about 20 wt %; preferably lessthan about 19 wt %; more preferably less than about 18 wt %; for examplefrom about 15 wt % to about 20 wt %; or about 16 wt % to about 20 wt %.Naturally the LOI value will be affected by the type and amount of thespecific chelating agent added as well as the residual moisture in thecatalyst. Consequently, LOI values lower than 15 wt % may be achievableusing the methods of the present invention, for example, as low as about12, 13 or 14 wt % to about 20 wt % In each instance, the level of LOIachieved should be such that the amount of chelating agent desired inthe finished catalyst has not been significantly adversely reduced,either through degradation and/or volatilization as a result of theheating process, but a significant amount of most of the residual waterpresent in the wet catalyst following impregnation has been driven off.As discussed above, it is desirable to retain about 85% to about 95% ofthe chelate in or on the catalyst after heating. Compared to catalystshaving the same composition and prepared in the same way except heatedto the lower temperatures of the prior art, the catalysts of the presentinvention typically exhibit a moisture content that is about one-thirdto about one-fourth the prior art catalyst. Expressing the LOI criterionin another way, the LOI value following heating and compared to the wetcatalyst soon after preparation is typically about 50% lower; preferablyabout 56% lower; more preferably about 60% lower; still more preferablyabout 65% lower; for example, about 65% to about 70% lower or more.

A further alternative criterion for characterizing a suitable catalystprepared according to the methods of the present invention is todirectly or indirectly measure the water content of the catalyst afterheating. The catalyst of the present invention can exhibit a moisturecontent of about 3 wt % to about 6 wt %; for example about 3.0 wt % toabout 5 wt %; alternatively about 3.5 wt % to about 5 wt %; for example3.75 wt % to about 4.75 wt %. The methods of the present invention canachieve a reduction, compared to a “wet” catalyst soon afterpreparation, of greater than about 85%; preferably greater than about87%; more preferably greater than about 90%; for example, desirably areduction of about 85% to about 90%, or more. In comparison, a catalystof the same composition prepared in the same manner but heated to about250° F. exhibits an estimated moisture content of about 8 wt %,equivalent to only about a 70% reduction in moisture. Catalysts preparedaccording to the methods of the present invention can be expected toexhibit significantly reduced water content compared to catalystsprepared without elevated heating. For example, water content in thecatalysts prepared according to the present methods that is less than25% of that in product prepared according to prior art methods; animprovement ranging from about 15% to about 35% can be expected;alternatively about 25% to about 33%.

The catalysts according to the invention are particularly useful inhydrocarbon conversion processes comprising contacting a hydrocarbonfeedstock with a particulate catalyst under conditions of elevatedtemperature and elevated pressure with hydrogen, wherein the catalyst ismade according to the present invention. As generally described, suchcatalysts comprise at least one catalytically active metal from GroupVIB of the periodic table, at least one catalytically active metal fromGroup VIII of the periodic table, and phosphorus and a chelating agent,wherein the metals, phosphorus and chelating agent are carried on aforaminous carrier, and wherein the catalyst exhibits a reduced moisturelevel, e.g., about 4 wt % or possibly less.

Catalysts prepared according to the present invention can be used invirtually all hydroprocessing processes to treat a plurality of feedsunder wide-ranging reaction conditions, generally, for example, attemperatures in the range of about 200° to about 500° C., hydrogenpressures in the range of about 5 to 300 bar, and liquid hourly spacevelocities (LHSV) in the range of about 0.05 to 10 h⁻¹. The term“hydroprocessing” can encompass various processes in which a hydrocarbonfeed is reacted with hydrogen at elevated temperature and elevatedpressure (hydroprocessing reaction conditions), including hydrogenation,hydrodesulfurization, hydrodenitrogenation, hydrodemetallization,hydrodearomatization, hydroisomerization, hydrodewaxing, hydrocracking,and hydrocracking under mild pressure conditions, which is also referredto as mild hydrocracking.

More specifically, “hydroprocessing” as the term is employed hereinmeans oil refinery processes for reacting petroleum feedstocks (complexhydrocarbon mixtures) with hydrogen under pressure in the presence of acatalyst to lower: (a) the concentration of at least one of sulfur,contaminant metals, nitrogen, aromatics and Conradson carbon, present insaid feedstock, and (b) at least one of the viscosity, pour point, anddensity of the feedstock. In addition, color of the resulting oil may beimproved. Hydroprocessing includes hydrocracking,isomerization/dewaxing, hydrofinishing, and hydrotreating processeswhich differ by the amount of hydrogen reacted and the nature of thepetroleum feedstock treated.

Hydrofinishing is typically understood to involve the hydroprocessing ofhydrocarbonaceous oil containing predominantly (by weight of)hydrocarbonaceous compounds in the lubricating oil boiling range(“feedstock”) wherein the feedstock is contacted with solid supportedcatalyst at conditions of elevated pressure and temperature for thepurpose of saturating aromatic and olefinic compounds and removingnitrogen, sulfur, and oxygen compounds present within the feedstock, andto improve the color, odor, thermal, oxidation, and UV stability,properties of the feedstock.

Hydrocracking is typically understood to involve the hydroprocessing ofpredominantly hydrocarbonaceous compounds containing at least five (5)carbon atoms per molecule (“feedstock”) which is conducted: (a) atsuperatmospheric hydrogen partial pressure; (b) at temperaturestypically below 593.3° C. (1100° F.); (c) with an overall net chemicalconsumption of hydrogen; (d) in the presence of a solid supportedcatalyst containing at least one (1) hydrogenation component; and (e)wherein said feedstock typically produces a yield greater than about onehundred and thirty (130) moles of hydrocarbons containing at least aboutthree (3) carbon atoms per molecule for each one hundred (100) moles offeedstock containing at least five (5) carbon atoms per molecule.

Hydrotreating is typically understood to involve the hydroprocessing ofpredominantly hydrocarbonaceous compounds containing at least fivecarbon atoms per molecule (“feedstock”) for the desulfurization and/ordenitrification of said feedstock, wherein the process is conducted: (a)at superatmospheric hydrogen partial pressure; (b) at temperaturestypically below 593.3° C. (1100° F.); (c) with an overall net chemicalconsumption of hydrogen; and (d) in the presence of a solid supportedcatalyst containing at least one hydrogenation component.

Isomerization/dewaxing is typically understood to involvehydroprocessing predominantly hydrocarbonaceous oil having a ViscosityIndex (VI) and boiling range suitable for lubricating oil (“feedstock”)wherein said feedstock is contacted with solid catalyst that contains,as an active component, microporous crystalline molecular sieve, atconditions of elevated pressure and temperature and in the presence ofhydrogen, to make a product whose cold flow properties are substantiallyimproved relative to said feedstock and whose boiling range issubstantially within the boiling range of the feedstock.

For the treatment of hydrocarbon distillates, the operating conditionswould typically comprise a hydrogen partial pressure within the range ofabout 100 psia (13 atm) to about 3,000 psia (204 atm); an averagecatalyst bed temperature within the range of about 500° F. (260° C.) toabout 800° F. (426° C.); a LHSV within the range of about 0.25 volume ofhydrocarbon per hour per volume of catalyst to about 10 volumes ofhydrocarbon recycle rate or hydrogen addition rate within the range ofabout 300 SCFB (53.4 Nm³/m³) to about 8,000 SCFB (1,424 Nm³/m³).Preferred operating conditions for the hydrotreating of hydrocarbondistillates comprise a hydrogen partial pressure within the range ofabout 200 psia (13 atm) to about 2,000 psia (135 atm); an averagecatalyst bed temperature within the range of about 550° F. (288° C.) toabout 750° F. (398° C.); a LHSV within the range of about 0.5 volume ofhydrocarbon per hour per volume of catalyst to about 5 volumes ofhydrocarbon per hour per volume of catalyst; and a hydrogen recycle rateor hydrogen addition rate within the range of about 500 SCFB (89 Nm³/m³)to about 6,000 SCFB (1,069 Nm³/m³).

The most desirable conditions for conversion of a specific feed to apredetermined product, however, can be best obtained by converting thefeed at several different temperatures, pressures, space velocities andhydrogen addition rates, correlating the effect of each of thesevariables and selecting the best compromise of overall conversion andselectivity. The catalyst composition of the invention is particularlysuitable for hydrotreating hydrocarbon feedstocks, in particularfeedstocks with less than 50 liquid volume % boiling above about 1050°F. (565.6° C.) as determined by ASTM D1160 distillation.

EXAMPLES Example 1

(A) A cobalt-containing catalyst solution is prepared as follows: (1)add 500 ml of water to an appropriate flask equipped with stirrer; (2)add 71.9 grams of anhydrous citric acid; and (3) add 156.7 grams ofcobalt carbonate (46% cobalt). Slowly add 57.5 grams of phosphoric acid(85%) followed by 501.3 grams of molybdenum trioxide and begin heatingto about 190° F. to 200° F. Heat at least at 190° F. for at least 2.5hours until the solution clears. Once the solution is clear it is cooledto below 130° F. and 251.6 grams of citric acid are added and themixture is stirred until the solution is clear. Thereafter the solutionis cooled to room temperature and diluted. The final MoO₃ concentrationis 0.50 grams per ml of solution. The amounts described provide for anexcess of citric acid of about 3 wt % since the heating step thatfollows can degrade or decompose a portion of the added citric acid andthe excess can insure that the desired amount is present in the finalcatalyst composition. If no excess is used, the second addition ofcitric acid is reduced to 241.5 grams (for a total addition of 313.4grams). The solution exhibits the following component ratios: citricacid/(CoO+MoO₃) (mol/mol): (with an excess)=0.36; and (without anexcess)=0.35. Analysis of the resulting catalyst showed the followingcomposition (metals expressed as the oxides; concentration in wt % on adry basis): CoO, 4.4 wt %; P₂O₅, 1.7 wt %; MoO₃, 24.0 wt %.(B) A nickel-containing catalyst solution is prepared as follows: (1)add 450 ml of water to a flask equipped with stirrer; (2) add 107.8grams of anhydrous citric acid; and (3) add 160.4 grams of cobaltcarbonate (49% nickel). Slowly add 77.1 grams of phosphoric acid (75%)and heat to 170° F. Add 501.3 grams of molybdenum trioxide and continueheating to about 210° F. for at least 3 hours until the solution clearsand after clearing cool to below 130° F. Add 77.1 grams of phosphoricacid (75%) and 251.6 grams of citric acid. Stir until the solution isclear, cool to room temperature and dilute to 1000 ml. The finalconcentration of MoO₃ is 0.50 grams per ml of solution. As above for thecobalt containing solution, the amounts described provide for an excessof citric acid of about 4 wt % since the heating step that follows candegrade or decompose a portion of the added citric acid and the excesscan insure that the desired amount is present in the final catalystcomposition. If no excess is used, the second addition of citric acid isreduced to 236.6 grams (for a total addition of 344.5 grams). Analysisof the resulting catalyst showed the following composition (metalsexpressed as the oxides; concentration in wt % on a dry basis): NiO,5.0; P₂O₅, 4.2; and MoO₃, 25.0. The solution exhibits the followingcomponent ratios: The solution contains the following component ratios:citric acid/(NiO+MoO₃) (mol/mol): (with an excess)=0.39; and (without anexcess)=0.37. The metals-containing solution of (A) is contacted with analumina carrier and the solution of (B) with a 3% silica/alumina carrierhaving the following characteristics: Surface Area (m²/gm), (A) 300, (B)310; N₂ Pore Volume (cc/gm), (A) 0.70, (B) 0.80; Loss on Ignition (wt %@1020° F.), (A) <3.0, (B) <2.0; and water pore volume (A) 0.8, (B) 0.9.(C) A cobalt-containing catalyst is prepared using malic acid as thechelating agent as follows: add 450 ml of water to a flask equipped withstirrer. With stirring, add 60 grams of malic acid, 158.1 grams ofcobalt carbonate, and 57.5 grams of 85% phosphoric acid and heat toabout 170° F. Add 500 grams of molybdenum trioxide and heat to 190-200°F. Continue heating for about 2 hours. Cool the solution to below 130°F. and add 163 grams of malic acid. Stir until solution clears. Cool anddilute to 1000 ml with water. The concentration of MoO3 is 0.5 grams/mlof solution. The metals-containing solution is contacted with a 3%silica/alumina carrier having the following characteristics: SurfaceArea (m²/gm), 292; N₂ Pore Volume (cc/gm), 0.80; Loss on Ignition (wt %@1020° F.), <2.0.(D) In this preparation, 200 grams of the carrier described above werecontacted with 147.1 ml of the solution from Example (C) and 20.9 ml ofwater. Analysis also showed 25.6% MoO3, 4.8% CoO, and 2.0% P2O5 on a dryweight basis. The resulting material was dried at about 400-410° F. asdescribed above. Analysis of the catalyst showed 15.7% LOI.(E) A cobalt-containing catalyst was prepared as follows: add 400 ml ofwater to a 2000 ml flask equipped with stirrer. Add 90 grams citric acidand 117.2 grams of cobalt hydroxide. Begin heating and add 57.5 grams of85% phosphoric acid. Add 500 grams of molybdenum trioxide. Heat theresulting mixture to 200° F. Continue heating at 200° F. for at least 2hours. Cool the solution to 100° F. and add 226 grams of citric acid.Stir until solution clears. Cool and dilute to 1000 ml with water. Theconcentration of MoO₃ is 0.5 grams/ml of solution.(F) The solution from Example (E) was used to impregnate metals and achelate on a carrier by the dip-soak method.

Dip 1 Dips 2+ Carrier Weight (gm) 175.0 175.0 Metals Solution 981 185Weight (gm) Diluted Volume of 780 780 Metals Solution (ml) Composition:Finished Catalyst (dry weight basis) Wt % CoO 3.0 3.4 Wt % MoO₃ 25.924.2 Wt % P₂O₅ 2.8 2.3The product from each dip is transferred to a rotary calciner and driedto about 400° F. as described above. Analysis of the catalyst showed thefollowing composition: 23.5% MoO3, 4.1% CoO, and 2.0% P2O5 on a dryweight basis. A sample taken after several dips was dried as describedabove and exhibited an LOI of 14.0%.(G) Metals are added to the carrier by various methods, including theincipient wetness and dip-soak methods. For the incipient wetness method200 grams of support are used. A volume of metals solution is used suchthat when applied to the support the target oxides will be achieved.Prior to contacting the metals solution with the support the metalssolution is diluted with water such that the resulting solution is equalto the water pore volume of the support. The metals solution iscontacted with the support for 1 hour. The resulting material is placedin a rotary calciner, which has been preheated to 320° F. The mixture isheld at 320° F. for 10 minutes. The material is heated under flowing airas the temperature is ramped up (such heating can take about 30 to about40 minutes). When the catalyst bed temperature reaches about 400° F., itis held at 400° F. to 420° F. for less than or equal to 10 minutes andthen immediately cooled to room temperature.

Using the dip-soak method in the laboratory, 175 grams of support areused and the total diluted dip solution is 780 ml. In the first dip themetals solution is the most concentrated. In subsequent dips only enoughmetals solution is added to match the theoretical amount needed totarget the desired metals' loading on the carrier. The support is placedin a basket with mesh sides and bottom to allow the solution topenetrate. The following results are based on the first four dips of anickel-containing catalyst preparation. The basket containing thesupport is immersed in the diluted metals solution for 50 minutes andduring this time the solution is recirculated through the basket toensure good contact with the support. The basket is removed from thesolution and the material is allowed to drain for 20 minutes. Thematerial is then transferred to a rotary calciner and dried as describedin the pore volume method. In each dip, except the first, the weight ofthe metals solution is the theoretical amount of metals needed to reachthe target oxide levels for 175 grams of carrier.

Dip 1 Dip 2 Dip 3 Dip 4 Carrier Weight (gm) 175.0 175.0 175.0 175.0Metals Solution 997.1 221 221 221 Weight (gm) Diluted Volume of 780 780780 780 Metals Solution (ml) Composition: Finished Catalyst (dry weightbasis) Wt % NiO 3.5 3.8 3.9 4.0 Wt % MoO₃ 25.3 25.5 24.6 24.3 Wt % P₂O₅5.6 5.4 5.2 5.1(H) Additional catalysts were prepared as described above by eitherincipient wetness or dip-soak method. Metals ratios vary to demonstratethat the method of making the catalyst solutions is flexible fordifferent amounts of raw materials. Catalysts that were dried at about400° F. exhibit LOI values of less than about 16 wt % whereas catalyststhat were dried at the lower temperature exhibit LOI values of greaterthan 20 wt %.

Impregnation Heating LOI MoO₃ P₂O₅ CoO NiO Catalyst Method ° F. Wt % Wt% Wt % Wt % Wt % I Dip-Soak 410 15.5 24.4 4.7 4.1 II Incipient >400 13.321.8 1.5 4.2 — Wetness III Dip-Soak 405 16.1 25.5 4.9 — 4.5 IV Incipient<250 22.9 17.4 5.8 — 5.3 Wetness V Dip-Soak <250 20.9 23.4 1.7 4.2 —

Example 2

A sample of the cobalt-containing supported catalyst prepared as inExample 1 was removed after it was prepared and tested for Loss onIgnition (LOI), a measure of the total volatiles present in the sample,essentially water and the organic chelating agent. The LOI test isconducted by subjecting a sample to an oxygen-containing atmosphere for1 hour at 1020° F. (548.9° C.). A further sample of the original wetcatalyst was placed in a rotary calciner and heated to progressivelyhigher temperatures up to 400° F. (204.4° C.). Small portions of thecatalyst were removed during heat-up and analyzed for weight loss by LOIand carbon content (wt %) using the “Leco” test instrument (LECOCorporation, Joseph, M I). In this test method an aliquot of sample isplaced in a ceramic crucible which is heated to over 2000° F. in astream of pure oxygen. The carbon is combusted to carbon dioxide and theoxygen-carbon dioxide gas mixture is passed into an Infrared detectorwhere the carbon dioxide content is measured. The percent carbon for thesample is automatically calculated by the analyzer. Initially, thecatalyst was placed in the rotary calciner at 175° F. After 1.5 hours asample was taken for analysis. The temperature was increased to 250° F.and held for 0.5 hour and a further sample was taken for analysis. Thetemperature was then raised to 300° F. and held for 0.5 hour after whicha sample was taken for analysis. This was repeated at 350° F. andfinally at 400° F. For the samples subjected to the LOI test,temperature was measured in the catalyst bed; for the carbon contenttest, in the furnace wall. The test results are shown in the followingtable.

Drying Temperature Loss on Ignition Carbon (° F.)/(° C.) (wt %) (wt %)None (as made, wet) 39.5 2.80 175/79.4  27.2 3.11 250/121.1 20.3 3.33300/148.9 17.5 3.71 350/176.7 15.6 3.70 400/204.4 13.6 3.67

It can be seen that as the heating temperature was increased the LOIvalues decreased indicating that the moisture was substantially drivenoff, and at the highest temperatures the volatiles content appears to beapproaching a constant value. Extrapolating the data to about 450° F., atemperature at which essentially all of the moisture would be removed,it appears that the catalyst prepared in this example would have about12 wt % of a material that can be lost on ignition and such material islikely the hydroxycarboxylic acid component, citric acid. Based on theabove data and assuming that little, if any, of the chelating agent islost during the heating process, the methods of the present inventioncan remove about 96 wt % of the moisture originally present in thesample whereas the method of the prior art, in which a catalyst istypically heated to about 250° F., results in removal of only about 48.6wt % moisture. Further, it can be seen that the carbon content valuesreached a fairly constant level, especially at the higher temperatureswhere less moisture was present in the samples.

These data suggest that moisture can be substantially removed from acatalyst sample without significant loss of the hydroxycarboxyliccomponent by judicious control of the heating conditions, particularlytemperature.

Example 3

For this comparison test, cobalt-containing catalyst samples prepared asdescribed in Example 1 were heated to about 250° F. (121.1° C.) forabout 10 minutes. The sample for high temperature treatment was thenramped up to about 410° F. (210° C.) and held at this temperature forabout 10 minutes, then cooled rapidly. The overall treatment time(including heat up and cool down) for the high temperature sample wasabout 1 hour. Temperatures were measured by a thermocouple in thecatalyst bed during drying. The catalyst samples were then used forevaluating hydrodesulfurization (HDS) and hydrodenitrogenation (HDN)performance with a hydrocarbon oil. Test conditions and results areshown in the following table.

Test conditions Value Feed Straight Run (SR) Diesel Total pressure, psig800 LHSV 1.5 H2/Oil, SCFB 1200 Feedstock API gravity 33.7 Sulfur, wt %0.57 Nitrogen, ppm 221 Heating Conditions Test Results* 250° F. 410° F.RVA HDS 100 100 RVA HDN 100 96 *RVA = Relative Volume Activity based onthe rate constant for the indicated process, HDS or HDN.

It can be seen that catalyst performance was essentially unaffected, butthe catalyst containing a lower level of moisture would be muchpreferred in use since it could be used substantially as received orwith significantly less effort to remove unwanted moisture prior toprocessing feedstock.

Example 4

Five hydroprocessing catalysts prepared according to the methods of thepresent invention were tested in order to characterize the volatilecompounds evolved when each was heated to 200° C. (392° F.). The majorgases generated were water vapor and carbon dioxide.

Catalyst Identification

(1) Cobalt-containing catalyst according to the composition described inExample 1. Catalyst bed temperature during the heating step=411° F.;LOI=15.4 wt %

(2) Same as (1) LOI−17.3 wt %

(3) Cobalt-containing catalyst sample according to the compositiondescribed in Example 1, but in the absence of further heating; LOI=22.6wt %

(4) Same as (3) LOI=22.7 wt % (5) Same as (3) LOI=23.5 wt %

Analytical Methodology

Volumetric Karl Fischer titration was used to identify and quantify thespecies evolved as the catalysts were heated following theirpreparation. Karl Fischer titration was conducted as follows:approximately 1 gram of each catalyst was introduced to a gas-tight ovenunder constant reducing gas sweep (about 100 cc/min). The sweep gaspassed through a midget ethylene glycol scrubber to trap evolvedmoisture and a portion of the glycol was titrated with Karl Fischerreagent at 30 minute intervals. The oven temperature was initially setat 100° C. and gas-scrubbed for 1 hour, at which time temperature wasincreased to 200° C. for 1 hour at the higher temperature.

Observations and Results

Karl Fischer Titration: When heated to 100° C. the high temperaturetreated catalyst samples yielded approximately one-quarter the weight ofwater as compared to low temperature treated samples, whereas furtherheating at 200° C. the difference decreased to 1:3 (see Tables 1 and 2below). Citric acid reduction made a significant contribution to theamount of water evolved when the samples were heated at 200° C. In allcases for both catalyst types a greater amount of water was generatedduring the first 30 minutes at each temperature as compared to thesecond 30 minute segment.

TABLE A Wt % Water by Karl Fischer Titration-Cumulative Versus TimeCumulative Wt % Water Evolved 0-30 min 30-60 min 60-90 min 90-120 minCatalyst at 100° C. at 100° C. At 200° C. at 200° C. (1) 0.9 1.4 2.9 3.6(2) 0.6 1.1 3.3 4.2 (3) 2.5 4.6 8.9 9.5 (4) 2.8 5.3 9.5 10.4 (5) 3.7 5.59.1 11.4

TABLE B Wt % Water by Karl Fischer-Per Time/Temperature Segment Wt %Water Evolved per Time Segment 0-30 min 30-60 min 60-90 min 90-120 minCatalyst at 100° C. at 100° C. at 200° C. at 200° C. (1) 0.9 0.5 1.5 0.7(2) 0.6 0.5 2.2 0.9 (3) 2.5 2.1 4.4 0.6 (4) 2.8 2.5 4.1 0.9 (5) 3.7 1.83.6 2.3

The test results clearly demonstrate that the catalyst preparationmethods of the present invention produce a catalyst having asignificantly reduced level of moisture, particularly when the catalystsamples are subjected to a level of heating following preparation thatdrives off moisture for analytical purposes but does not causeadditional degradation of the incorporated citric acid.

Example 5 (Comparative)

Three hydroprocessing catalysts prepared without additional heating atelevated temperature (samples heated to 200-250° F.) were tested inorder to characterize the composition and volatile compounds present inthe samples. These results provide compositional reference points forcomparative purposes.

Catalyst Sample Cobalt Nickel Nickel Chelate Citric Acid None CitricAcid Test Wt % Carbon (a) 4.5 0.06 5.0 Wt % as Citric Acid (b) 12.0 0.1613.3 Wt % Water-TKF (c) 6.6 9.5 7.3 Wt % Water-CKF (c) 7.3 10.3 7.7Total Volatiles 22 14 24 @600° C. (d) Total Volatiles 29 27 35 @1000° C.(d) (a) Wt % Carbon by CHN Analyzer (b) Wt % Citric Acid = Wt % Carbon ×2.668 (c) Catalysts extracted with dry methanol and the extractsanalyzed by Karl Fischer techniques: T = titrimetric; C = coulometric(d) Total volatiles at temperature for 4 hours

These data confirm that catalyst samples prepared according to the priorart include relatively high amounts of moisture.

All documents described herein are incorporated by reference herein,including any priority documents and/or testing procedures. Theprinciples, preferred embodiments, and modes of operation of the presentinvention have been described in the foregoing specification. Althoughthe invention herein has been described with reference to particularembodiments, it is to be understood that these embodiments are merelyillustrative of the principles and applications of the presentinvention. It is therefore to be understood that numerous modificationsmay be made to the illustrative embodiments and that other arrangementsmay be devised without departing from the spirit and scope of thepresent invention as defined by the appended claims. Further, any rangeof numbers recited in the specification or paragraphs hereinafterdescribing various aspects of the invention, such as that representing aparticular set of properties, units of measure, conditions, physicalstates or percentages, is intended to literally incorporate expresslyherein by reference or otherwise, any number falling within such range,including any subset of numbers or ranges subsumed within any range sorecited.

1. A method for preparing a hydroprocessing catalyst comprising: (I)providing at least the following components: (A) at least one calcinedforaminous carrier having a water pore volume; (B) catalytically activemetals useful in hydroprocessing hydrocarbons, said metals in the formof at least one component providing at least one metal from Group VIB ofthe periodic table and at least one component providing at least onemetal from Group VIII of the periodic table; (C) at least one chelate;(D) water in a quantity sufficient to form a solution or dispersioncomprising said catalytically active metals and said at least onechelate; and (E) optionally, at least one phosphorus-containing acidiccomponent; (II) contacting said components (I)(A) with said solution ordispersion comprising (I)(B), (I)(C), (I)(D) and optionally (I)(E) for atime and at a temperature sufficient to form a mixture and to impregnatesaid carrier with a suitable amount of said components (I)(B) and (I)(C)and optionally (I)(E); (III) to the extent that the volume of saidsolution or dispersion equals or exceeds the water pore volume of saidcarrier separating said impregnated carrier from said excess solution ordispersion; and (IV) heating said impregnated carrier to a temperaturehigher than 200° C. and less than a temperature and for a period of timethat would cause substantial decomposition of said at least one chelate.2. The method of claim 1, wherein said at least one metal from Group VIBis selected from the group consisting of molybdenum and tungsten andwherein said at least one metal from Group VIII is selected from thegroup consisting of cobalt and nickel.
 3. (canceled)
 4. The method ofclaim 1 wherein said chelate is selected from the group consisting ofhydroxycarboxylic acids, ethylene glycol, glycerol, ethanolamine,polyethylene glycol, hydroquinone, ethylenediamine,ethylenediamine-tetraacetic acid, cysteine, alanine, methionine,gluconic acid, pyridine-2,3-dicarboxylic acid, thiophene-2-carboxylicacid, mercapto succinic acid, nicotinic acid, lactose, andacetone-1,3-dicarboxylic acid.
 5. The method of claim 4, wherein said atleast one hydroxycarboxylic acid is selected from the group consistingof glycolic acid, hydroxypropionic acid, hydroxybutyric acid,hydroxyhexanoic acid, tartaric acid, malic acid, glyceric acid, citricacid and gluconic acid.
 6. The method of claim 1 wherein said foraminouscarrier is at least one member selected from the group consisting ofsilica, silica-gel, silica-alumina, alumina, titania, titania-alumina,zirconia-alumina, zirconia, boria, terrana, kaolin, magnesium silicate,magnesium carbonate, magnesium oxide, activated carbon, aluminum oxide,precipitated aluminum oxide, activated alumina, bauxite, kieselguhr,pumice, natural clays, synthetic clays, cationic clays or anionic clayssuch as saponite, bentonite, kaolin, sepiolite or hydrotalcite, andmixtures thereof.
 7. The method of claim 1 wherein said heating iscarried out according to a condition selected from the group consistingof: (A) at greater than about 204° C.; (B) for less than about 1 hour;(C) for a time and temperature sufficient to provide a catalystexhibiting a moisture content of about 3 wt % to about 6 wt %; andcombinations thereof.
 8. (canceled)
 9. The method of claim 1 wherein:(A) the molar ratio of said Group VIII metal to Group VIB metal is about0.05 to about 0.75, and wherein said Group VIII metal component isprovided by a substantially water insoluble component; or (B) whereinsaid at least one phosphorus-containing acidic component issubstantially water soluble and is present in an amount sufficient toprovide an elemental phosphorus to Group VIB metal molar ratio of about0.01 to about 0.80.
 10. (canceled)
 11. The method of claim 7 whereinsaid heating is carried out for a time and temperature sufficient toprovide a catalyst exhibiting a loss in weight on ignition (LOI) of lessthan about 20 wt %.
 12. (canceled)
 13. The method of claim 1 whereinsaid heating is carried out for a time and temperature sufficient toprovide a catalyst exhibiting a reduction in moisture content, comparedto the wet catalyst following preparation of greater than 90% andwherein the catalyst is not calcined following heating.
 14. The methodof claim 1 wherein the amount of hydroxycarboxylic acid on theimpregnated foraminous carrier prior to heating exceeds the amountdesired in the catalyst after heating by about 1 wt % to about 10 wt %.15. The method of claim 5, wherein said hydroxycarboxylic acid is citricacid.
 16. The method of claim 1, wherein at least onephosphorus-containing acidic component is phosphoric acid ororthophosphoric acid.
 17. A hydroprocessing catalyst prepared by themethod of claim
 1. 18. A hydroprocessing catalyst prepared by the methodof claim
 7. 19-20. (canceled)
 21. The hydroprocessing catalyst of claim17, wherein said at least one organic chelate compound comprises about0.05 to about 5 times the molar amount of said catalytically activemetals; and wherein said catalyst exhibits a moisture content of about 3wt % to about 6 wt %.
 22. The catalyst of claim 21 wherein said organicchelate compound is at least one hydroxycarboxylic acid.
 23. Thecatalyst of claim 22 wherein said at least one hydroxycarboxylic acid iscitric acid.
 24. The catalyst of claim 21 useful in hydroprocessing apetroleum feed, wherein said hydroprocessing compriseshydrodesulfurization and hydrodenitrification of hydrocarbons.
 25. Thecatalyst of claim 21 useful in hydrodesulfurization andhydrodenitrification of hydrocarbons.